Contribution à l'étude de la déformation de la paléomarge téthysienne dans les Alpes occidentales. Analyses tectoniques et microtectoniques dans la zone des brèches de Tarentaise ( région de Moutiers) et dans les schistes lustrés du Mont Jovet . Alpes françaises

摘要

This study concern the structures and the deformation of the "Breches de Tarentaise" zone and the Mont Jovet "schistes lustres" klippe, in the Moûtiers area (Northern part of French Alps). Three methods of study are need : geometric analysis, quantitative analysis and modelization. 1- Geometric analysis Shown in geologic map at the scale of 1/25.000 : - The Breches de Tarentaise zone, in the Moûtiers region belongs to a passage of fracturation which was generated after the polyphase folding so that it is very difficult to superpose the paleogeographic framework on the actual tectonic comportement. - The Mont Jovet klippe and its basal gypsum cushion are conserved in the interior of a collapsing zone, oriented sensitive NNE-SSW and formed with many juxtaposed blocks . . At meso and micro-structure scale : - The analysis of striation (by the "diedres droits" Method Angelier, 1977) essentially developed on the fault planes of the carboniferous sandy layers in the houillere briançonnaise zone relative autrochtonous to the Mont Jovet klippe, shows in the diagrams that 01 is around N 120° E. We notice that sens of movement of faults in the Moûtiers region is compatible with this direction. - Based on the princirle of superposition of folding phases, three synschistose foldings are found. Field evidences support the caracteristics of progressive deformation in the shear zone for the phase 2 and phase 3. The sheath folds were developed during the phase II deformation. 2- Quantitative analysis. In the flysch of "IBreches de Tarentaise" zone in the Moûtiers region, the analysis of fibrous vein arrays which developed during or just after the synschistose deformation (II and III), indicate an extension rate varis close to 40 and 45 %. in the direction of N 30° E. In the. permien "verts et violets',' schist of the same zone, the deformatlon elllpsolde, of the phase II, is ellongated like a cigar paralle 1 to the P2 axes. The ratios of axes know from mesuring are X/Z = 9,8 and Y/Z = 1,5. 3- The analogic modelization. The models made under the condition of bulk simple shear and bulk pure shear confirm the progressive deformation processes and the formation of active folds.